Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.76	3.641%	$218.4338	$218.43	$218.45	$218.40
Purchase #2	$199.26	6.602%	$212.4151	$212.42	$212.40	$212.40
Purchase #3	$142.87	11.617%	$159.4672	$159.47	$159.45	$159.50
Purchase #4	$142.78	6.869%	$152.5876	$152.59	$152.60	$152.60
Purchase #5	$190.61	3.119%	$196.5551	$196.56	$196.55	$196.60
Purchase #6	$155.51	12.371%	$174.7481	$174.75	$174.75	$174.70
Purchase #7	$213.40	3.331%	$220.5084	$220.51	$220.50	$220.50
7 purchase totals =	$1,255.19		$1,334.7153	$1,334.73	$1,334.70	$1,334.70